In a conventional gas turbine engine, a compressor introduces air into a combustion chamber in which the air is mixed with the burning fuel to produce flue gases that drive a turbine in the exhaust portion of the engine. The efficiency of such a turbine design is correlated to the operating temperatures of the system. To maintain operating temperature below a maximum operating temperature (i.e., the temperature at which the system fails), additional air is introduced into the combustion chamber, such that the fuel to air ratio in the combustion chamber is maintained below the point at which stoichiometric combustion of the fuel is achieved. Thus, the additional air serves to maintain the gases below the maximum operating temperature. One of the drawbacks of this process, however, is that the energy needed to compress this additional air reduces the overall efficiency of the engine.
This observation has led to gas turbine designs in which steam and/or water is injected into the combustion system. For example, Dah Yu Cheng (U.S. Pat. Nos. 3,978,661, 4,128,994 and 4,297,841) recognized that steam addition to the Brayton cycle can significantly increase the power and efficiency of the engine provided heat is recovered from the exhaust gases. Unfortunately, the amount of heat that leaves the system in the exhaust gases also increases when steam is used. The exhaust gases generated in a steam injected engine leave at a higher temperature and have a higher specific heat. Hence, in the absence of some form of heat recovery system, the overall efficiency of the engine decreases.
Further gas turbine designs have included processes for recovering water from exhaust or flue gases and re-using the water in the gas turbine, as described above. The composition of modern gas turbine engines, however, cannot adequately withstand the introduction of corrosive substances and like materials. Therefore, gas turbine engine designs of this type have required a chemical water treatment apparatus to treat or distill the water before it is introduced back into the gas turbine engine, as taught by Inage (U.S. Pat. No. 7,594,387). The addition of a water treatment module, however, increases the complexity, maintenance and operating costs of the resulting gas turbine engine system.
Therefore, a need exists to overcome the problems with the prior art as discussed above, and particularly for a more effective and efficient process for extracting and using water from flue gases of a gas turbine engine.